She gave a surprise performance of Leonard Cohen’s “Hallelujah” when an audience member offered up $10,000 if she crooned the tune.

Tony winner Brian Stokes Mitchell appeared onstage at the Brooks Atkinson Theatre after Friday’s show and announced that an anonymous donor in the crowd would put up the dough for charity the Actors Fund if lang sang the song she’d previously performed at the closing ceremonies of the 2010 Winter Olympics.

Our spy said she “sang the number to perfection,” but didn’t come back onstage after the encore, despite the cheers. We hear the mystery donor was Steiner Equities Group’s David Steiner.